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Home » Water Management in Mature Oil Fields using Advanced Particle Gels

Water Management in Mature Oil Fields using Advanced Particle Gels

Mojdeh Delshad

Excess water production is a major problem leading to early well abandonment and unrecoverable hydrocarbons for mature wells. The ultimate purpose of the project is to provide a simulation tool to optimize particle gel treatments to increase oil recovery and reduce water production.

However, the current technology has limitations and the results of these treatments have been sporadic and unpredictable. A recent interest in gel treatments uses particle gels to overcome some of the distinct drawbacks inherent in in-situ gelation systems. This project will provide a better understanding of recent particle gel processes based on systematic laboratory experiments and will develop a numerical tool to solve excess water production taking into account the reservoir heterogeneity and operating conditions. The ultimate purpose of the project is to provide a simulation tool to optimize particle gel treatments to increase oil recovery and reduce water production. This has direct economic benefits by increasing income and saving routine operating costs, in addition a reduction in the water production rate serves to decrease the injection water usage and associated environmental risks.

Excess water production is a major problem leading to early well abandonment and unrecoverable hydrocarbons for mature wells. Current remedies of gel treatments of injection wells to plug thief zones are cost-effective methods to improve sweep efficiency in reservoirs and reduce excess water production during hydrocarbon production. However, the current technology has limitations and the results of these treatments have been sporadic and unpredictable. A recent interest in gel treatments uses particle gels to overcome some of the distinct drawbacks inherent in in-situ gelation systems. This project will provide a better understanding of recent particle gel processes based on systematic laboratory experiments and will develop a numerical tool to solve excess water production taking into account the reservoir heterogeneity and operating conditions. The ultimate purpose of the project is to provide a simulation tool to optimize particle gel treatments to increase oil recovery and reduce water production. This has direct economic benefits by increasing income and saving routine operating costs, in addition a reduction in the water production rate serves to decrease the injection water usage and associated environmental risks.

Scope of Work

The purpose of the project is to develop a mechanistic understanding of preformed microgel systems to that are used to reduce water production and improve oil recovery, to gain a better understanding of the process, and create a simulation tool for design and optimization of the microgel water shutoff process.

Coreflood experiments will help in understanding the prevailing mechanisms of preformed particle gel transport in porous media. The experiments will provide the necessary data to develop and validate mechanistic models for each process that will be implemented in a reservoir simulator to design and predict the performance of such treatments in field projects. The proposed research includes designing and performing experiments, development of mathematical models and a water shut off reservoir simulator, validation and verification, and feasibility of the proposed treatment for a particular field. The simulator will aid in providing guidelines for the application in candidate reservoirs.

Technical Tasks

Task 5 - The objective of this task is to enhance our understanding of gel flow and transport and conformance control mechanisms.

Subtask 5.1 - The passing/blocking rules of different strength particles through pores and fractures will be identified and evaluated using a newly-designed experimental model. We will put swelling gel particles on top of the screen plate and gradually increasing the pressure until particles pass through the holes or fissures. The maximum pressure that pushes particles out of holes will be the threshold pressure of a particle moving through a throat or an open fracture.

Subtask 5.2 - Sandpack experiments will be used to determine the effect of gel particles on the water and oil permeability. The injection pressure and permeability reduction factors for oil and water will be quantified as a function of particle strength and permeability.

Task 6 - This task will involve three subtasks. The first subtask is to identify a real reservoir that would be a good candidate for conformance control and obtain appropriate data to use in the lab experiments and simulations. The second subtask is to design and provide a cost estimate for experiments designed to mimic heterogeneity. The third subtask will be to conduct a series of experiments that will evaluate the performance of the microgel system and provide useful data for numerical models.

Task 7 - This task will develop models based on the results form Tasks 5 and 6. The mathematical models for flow and transport of gel will be implemented in the reservoir simulator. The models and their implementation in the simulator will be verified and validated agonist laboratory results.

Subtask 7.1 - This subtask is to build mathematical models to characterize particle gel flow and blocking behavior in different porous media. We will develop the mathematical model for the different types of microgels; such as preformed particle gel (PPG), colloidal dispersion gel (CDG), and Bright Water. Primarily, we will develop the following five mathematical predictive models:

Gel swelling ratio as a function of gel strength, salt concentration, and temperature.

Effective viscosity as a function of gel strength, rock/fracture permeability and injection rate.

Subtask 7.2 - Once the mathematical models using the results of the experiments discussed in Tasks 5 and 6 are developed, they will be implemented in the simulator and tested. Main activities are as follows:

Development of Bright Water gel model where the reaction between cross-linker and polymer will be considered. The viscosity, adsorption, and permeability reduction factor as a function of salinity, gel concentration, temperature, and other related parameters will be developed, tested using measured data, and implemented in the simulator.

Subtask 7.3 - The simulator will be tested against experimental data of Tasks 5 and 6. We will also setup test cases to demonstrate its capability for conformance control processes.

January 2014 Project Summary

Accomplishments

Open conduit models were used to understand the effect of gel particle size, injection rate and conduit conductivity on millimeter-sized particle injectivity and resistance factor. A mathematical model was developed to correlate resistance factor with theses parameters.

Sandpacks with the permeability of greater than 2 Darcy were used to study the effect of micro-gel particle size, injection rate, and permeability on micorgel injectivity and resistance factor.

Berea sandstone cores with the permeability less than 2 Darcy were used to evaluate the effect of rock permeability and gel concentration on submicro- and nano- gel resistance factor and oil recovery improvement.

Parallel heterogeneous sandpack models were built to study the effect of microgel on profile modification, water cut reduction, and oil recovery with different permeability contrast.

A new model for resistance factor and residual resistance factor with salinity effect was developed.

Gel transport models were implemented in a reservoir simulator (UTGEL) and validated against laboratory experiments.

Significant Findings

Millimeter-sized particle gels can significantly reduce the permeability of an open conduit by forming a gel-pack, where the permeability of gel-pack is a strong function of particle strength but a weak function of particle size and conduit opening size.

Large particles have a lower permeability than smaller particles across all of the load pressure ranges.

Both Fr and Frr increase with particles concentration but decrease with flow rate.

PPG flood simulations were performed in layered reservoirs with different contrast in permeabilities. The simulation results indicated that the higher the permeability contrast, the greater the benefit of PPG injection.

Future work:

The effect of load pressure on gel pack permeability as a function of oil viscosity will be studied oil viscosity of 1.5, 37, and 195 cp.

Effect of permeability will be studied on microgel Fr and Frr.

Determined of the particle size distribution before and, if possible, after extrusion.